This invention relates to polyol condensation.
Polyol condensation products, such as diglycerine, are known constituents of drilling fluids. However, it is desired to produce drilling fluid additives with greater ability to prevent shale dispersion, improve wellbore stability, reduce fluid loss and reduce filter cake thickness. Cyclic ethers per se are disclosed as being produced by condensing an alcohol having an ester or ether group (rather than just an alcohol) in Dreyfus, U.S. Pat. No. 2,062,404 (Dec. 1, 1936). It is shown in Selden et al., U.S. Pat. No. 3,968,169 (Jul. 6, 1976) that glycerine can be condensed with an acid catalyst to give linear di- and tri-glycerol with a small amount of cyclic di- and tri-glycerol byproduct being produced. Alkali catalyzed condensation of glycerol to produce diglycerol and higher polyglycerols is disclosed in Alsop, U.S. Pat. No. 2,487,208 (Nov. 8, 1949). However, in fact, it requires very precise control of the alkali condensation reaction of a polyol to get a cyclic structure without getting undesirable reactions including, in the worst case, toxic acrolein. Alsop attempts to inhibit undesirable reactions by deactivating the catalyst halfway through the reaction.